• Male or female ≥ 18 years of age.

• Has a prior history of (h/o) MM (based on International Myeloma Working Group (IMWG) criteria) and now has evidence of relapsed or refractory MM. RRMM of progressive disease as defined by the IMWG 2006 and 2016 criteria (Kumar at al).

• Specific criteria for dose escalation and dose expansion:

∙ Phase 1 dose escalation: patients will be required to have TCE RRMM (including a proteasome inhibitor (PI) (≥ 2 cycles or 2 months of treatment), an immunomodulatory drug (IMiD)) (≥ 2 cycles or 2 months of treatment) and a CD38 antibody (≥ 2 cycles or 2 months of treatment) after receiving ≥ 3 prior lines of therapy. Prior BCMA exposure is allowed. (Subjects with discontinued PI/IMiD/Cluster of differentiation 38 (CD38) therapy due to severe adverse event after \< 2 months are allowed)

‣ Dose expansion cohort: RRMM patients will be lenalidomide refractory, TCE (exposed to IMiD, PI and CD38 antibody therapy (≥ 2 cycles or 2 months of treatment for each) and have received ≥ 2 prior lines of therapy. Prior BCMA targeted therapy is allowed, not required. (Subjects with discontinued PI/IMiD/CD38 therapy due to severe adverse event after \< 2 months are allowed. Lenalidomide refractory is defined as having evidence of progressive disease on lenalidomide (≥ 10 mg or greater, ≥ 21 days/28) or within 60 days of stopping lenalidomide therapy.)

• Has measurable disease defined as at least 1 of the following:

∙ Serum M-protein ≥ 0.5 g/dL (dose escalation) and 1.0 g/dL (dose expansion cohorts)

‣ Urine M-protein ≥ 200 mg/24 hours

‣ Serum free light chain (FLC) assay: involved FLC assay ≥ 10 mg/dL (≥ 100 mg/L) AND an abnormal serum FLC ratio (\< 0.26 or \> 1.65). (Can be used to fulfill the inclusion criteria of measurable disease in patients who do not have measurable disease by M-protein).

• Has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

• Has adequate baseline organ function, as demonstrated by the following:

∙ Calculated creatinine clearance \> 30 mL/min as assessed by the Cockcroft-Gault equation, Modification of Diet in Renal Disease (MDRD) equation (National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), 2015) or as assessed by 24-hour urine collection.

‣ Serum bilirubin ≤ 1.5 mg/dL, excluding Gilbert's.

‣ Aspartate transaminase (AST) and alanine transaminase (ALT) ≤ 2.5 × institutional upper limit normal (ULN).

‣ Total serum calcium (corrected for serum albumin) or ionized calcium within normal limits (WNL) (treatment of hypercalcemia is allowed and patients may enroll if hypercalcemia returns to WNL with standard treatment).

• Has adequate baseline hematologic function, as demonstrated by the following:

∙ Absolute neutrophil count (ANC) ≥ 1.0 x 10\^9/L (myeloid growth factors must not have been administered within 7 days (14 days for extended 1/2-life products).

‣ Hemoglobin ≥ 8 g/dL (red blood cell transfusions permitted provided the anemia is disease-related).

‣ Platelet count ≥ 100 x 10\^9/L and no platelet transfusions during the 7 days before first dose (without transfusions). (Dose expansion cohorts will be allowed to have platelets counts ≥ 75 x 10\^9/L with no platelet transfusions during the prior 7 days).

• Must have at least 2 negative serum beta-human chorionic gonadotropin (β-hCG) pregnancy test result obtained prior to initiating therapy. The first test should be performed within 10-14 days and the second within 24 hours prior to initiating therapy if the patient is a female of childbearing potential (FCBP; defined as a sexually mature woman who has not undergone a hysterectomy or bilateral oophorectomy or has not been naturally postmenopausal for at least 24 consecutive months).

• Men and women of childbearing potential must agree to not donate sperm and eggs (ova and oocytes) throughout study therapy and for 3 months after the last treatment.

⁃ Men and women agree to use acceptable contraceptive methods for the duration of time on the study, and continue to use acceptable contraceptive methods for 3 months after the last treatment with study treatment.

• Women of childbearing potential must agree to 2 methods of reliable birth control simultaneously while receiving study treatment and until 100 days after last dose of study treatment: one highly effective form of contraception (tubal ligation, intrauterine device, hormonal \[oral, injectable, transdermal patches, vaginal rings or implants\] or partner's vasectomy, and 1 additional effective contraceptive method (male latex or synthetic condom, diaphragm or cervical cap).

∙ Males must agree to always use a latex or synthetic condom during any sexual contact with females of reproductive potential.

⁃ All patients should be encouraged to be fully vaccinated prior to initiation of therapy including being up-to-date on vaccines against pneumococcus, yearly influenza, Coronavirus disease (COVID) booster(s), and any age appropriate vaccine. Live attenuated vaccines are not allowed while on study treatment or within 4 weeks of starting treatment.

⁃ Has provided signed informed consent before initiation of any study-specific procedures or treatment.

⁃ Must agree to, and be capable of, adhering to the study visit schedule and other protocol requirements, including follow-up for overall survival.